1. Field of the Invention
The invention relates to an adsorbent, supple, filter fabric as well as a method for its manufacture. More particularly, the invention relates to such filter fabrics which can be used as filtering components of ventilating systems and air conditioning equipment as well as, because of their flexibility, in clothing which is protective against dusty and gaseous hazardous materials.
2. Description of Related Art
German patent DE 33 04 349 C2 discloses a membrane filter, having an adhesive agent imprinted on the textile carrier material in uniform, punctiform distribution by means of a stencil as a pattern of little adhesive piles in the shape of a hemisphere or a cone. Adsorbent particles having a diameter of 0.1 to 1 mm are fixed on it, likewise in uniform, punctiform distribution. The punctiform pattern covers 30 to 70% of the carrier-material surface. The adhesive agent is a solvent-free polyurethane. The quantity of the adsorbent applied is stated with 10 to 200 g/m.sup.2.
To produce it, 30 to 70% of the surface of the carrier material is covered by means of a stencil with a punctiform pattern of little adhesive piles in the shape of a hemisphere or a cone. The adhesive is a mixture of a prepolymerized, masked isocyanate and a cross-linking agent. The imprinted surface is sprinkled with adsorbent particles and the adhesive agent is cross-linked.
A disadvantage of this filter fabric is that, in order to obtain sufficient permeability to air, the adsorbent particles are fixed only on the surfaces of the little adhesive piles. This limitation precludes an adsorbent coating above 200 g/m.sup.2. In particular, it is not possible to provide for further adsorbent layers. Consequently the quantity of pollutants able to be adsorbed spontaneously is also limited.
The fact that the adsorbent particles cannot mutually bond adhesively, but rather only directly to the little adhesive piles, also rules out the possibility of taking advantage of the higher permeability to air of adsorbent particles up to 5,000 .mu.m large and at the same time offering a large, spontaneously effective adsorbent surface. Given the suggested dimensions of the little adhesive piles having a height of 0.05 to 0.5 mm and a diameter of 0.2 to 1 mm, not enough binding agent is available for larger quantities of adsorbent particles.